Future large-scale space operations, including space hotels, solar power satellites, and orbital factories, will require volatiles such as water, methane, ammonia, and carbon dioxide.^* These materials can be used to produce propellant, metal for facility construction (such as nickel-iron alloy), semiconductors for manufacturing photovoltaic power systems (such as silicon, arsenic, and germanium), and simple mass for ballast and shielding. The cost to transport these commodities from Earth today is $10,000 per kilogram. In the future, the extraction of these materials from easy-access asteroids will become a competitive option.

All of these resources are present in asteroids. About 10 percent of the near-Earth asteroids (NEAs) are more accessible than the Moon, requiring a velocity increase (delta-v) from low Earth orbit of less than 6 kilometers per second (km/s; 3.75 miles per second) for rendezvous, with a return departure delta-v of 1 km/s or less. A few are extremely accessible, only...